The need to maintain, for example, the proper level of oil in an internal combustion engine is well known. Low oil levels can cause excessive wear and can even cause engine failure when such levels are exceedingly low. Most internal combustion engines are provided with a dipstick for checking the oil level in the oil pan of the engine. While the conventional dipstick provides an accurate indication of oil level when the engine is not running, it is virtually useless when the engine is running because of the turbulence and agitation of the oil in the oil pan. The necessity of shutting the engine down to check the oil level can be a significant problem with diesel engines in cold weather, because such engines are difficult to restart. Obviously, in the case of a motor vehicle, the dipstick is of no use at all while such vehicle is being operated. Further, many operators forget to check the dipstick before oil quantities have dipped to dangerously low levels. This can be a particular problem with over-the-road trucks which are driven hundreds of miles per day. In addition, a dipstick (which can only be used with the vehicle or other machine stopped and the engine shut down) does not provide any early warning of a major oil leak.
Many internal combustion engines are provided with oil pressure gauges and/or warning lights which indicate low oil pressure. While these devices will provide indication of very low oil levels, such as those caused by major leaks, the oil level has usually fallen to a level where the engine is being damaged before such indication is apparent. Moreover, such prior art devices generally only operate when the engine is running.
Prior art oil level monitoring devices have been provided which comprise oil level sensing units which are disposed in the conventional dipstick tube and/or the oil pan of an internal combustion engine. Some examples include those devices disclosed in U.S. Pat. Nos. 4,337,657 and 4,034,608. While these devices can provide an indication of oil level when the engine is not running, they, like the conventional dipstick, are inaccurate when the engine is running because of the agitation of the oil in the oil pan, and moreover, they do not take into account and compensate for the quantity of oil which is in circulation when the engine is running.
Other approaches to a solution of this problem include attaching a separate reservoir to an oil pan, the reservoir containing a mechanism for monitoring the oil level therein. U.S. Pat. No. 3,605,086 is one example of this art. However, prior to the present invention, devices using this type of art still contained an inherent inaccuracy, that being the difference between the level of oil in the pan with the engine running, with a quantity of oil being dispersed throughout the engine lubricating system, and the increased level present with the engine not running and the previously dispersed oil having been returned to the pan.
Therefore, it is a principal object of the present invention to provide an oil level monitoring device which is capable of providing a continuous indication of oil level in the oil pan of an internal combustion engine, (or other mechanical or hydraulic system) even when the engine is running and the vehicle or other device it powers is being operated.
It is a further object of the present invention to provide such an oil level monitoring device which will maintain its accuracy and compensate for the difference between the level of oil in a pan when an engine is running and that when the engine is not running.